1. Field of the Invention
The present invention relates to a planetary gear mechanism wherein planetary gears are efficiently lubricated.
2. Discussion of the Prior Art
A power transmission incorporating a planetary gear mechanism is known. Such a planetary gear transmission is widely used for motor vehicles and industrial machines and equipment. In particular, the planetary gear transmission is most commonly used as an automatic transmission for motor vehicles, owing to its comparatively high degree of smoothness in changing the speed reduction ratio during power transmission, and its comparatively small size. Further, a planetary gear mechanism is used as an auxiliary transmission coupled to a continuously variable transmission, as disclosed in laid-open Publications 60-252857 and 61-130656.
For example, the planetary gear mechanism of a planetary gear transmission includes a rotating shaft having a splined end portion, a sun gear splined at the free end of the splined end portion such that the sun gear is rotatable with the rotary shaft, a carrier rotatably supporting planetary gears which engage the sun gear, a ring gear engaging the planetary gears, and a clutch disposed between the rotating shaft and the carrier, for transmitting power between the rotating shaft and the carrier.
In the planetary gear mechanism constructed as indicated above, the clutch for connecting the rotating shaft and the carrier generally uses first friction means which is supported by a first rotary member rotating with the rotating shaft, and second friction means which is supported by a second rotary member rotating with the carrier. The first and second friction means are adapted to frictionally engage with each other for transmitting power between the first and second rotary members, i.e., between the rotating shaft and the carrier The first rotary member is also splined on the rotating shaft such that the first rotary member is adjacent to the sun gear at the free end of the splined portion of the rotating shaft.
Usually, there exists a certain amount of clearance between the splines of the splined end portion of the rotating shaft and the spline grooves of the sun gear. Therefore, the rotating shaft and the sun gear more or less suffer from an error in concentricity or a radial play therebetween, which causes various problems. For instance, the carrier cannot be precisely aligned with the sun gear, due to misalignment of the sun gear which arises from the above-indicated clearance. Usually, the first rotary member and the sun gear are first splined on the splined end portion of the rotating shaft. Then, the carrier is assembled to the sun gear, through a thrust bearing interposed therebetween, such that one of opposite axially extending annular retainer portions of the thrust bearing engages the boss or cylindrical portion of the carrier, while the other annular retainer portion engages the sun gear. If the sun gear is not accurately aligned with the axis of rotation of the rotating shaft, the thrust bearing which has been attached at one of its annular retainer portions to one of the sun gear and the carrier cannot be easily brought into engagement with the other of the sun gear and the carrier.
On the other hand, the radial clearance between the splines of the splined end portion of the rotating shaft and the spline grooves of the first rotary member and sun gear may be used as a passage for feeding a lubricant toward the free end of the rotating shaft. In this case, the lubricant may leak through a gap between the first rotary member and the sun gear, and the thrust bearing cannot be sufficiently lubricated.